Charles e



(No Model.)

C. E. CARPENTER.

ELECTRIC HEATING APPARATUS.

N 4 o 29 55'9 .3. Patenteadgl'nS, 1890 i UNITED STATES PATENT OFFICE.

CHARLES E. CARPENTER, OF MINNEAPOLIS, MINNESOTA, ASSIGNOR, BY DI- AND MESNE ASSIGNMENTS, TO THE CARPENTER-NEVENS ELEC- TRO-HEATING COMPANY, OF SAME PLACE.

ELECTRIC-HEATING APPARATUS.

SPECIFICATION forming part of Letters Patent No. 429,559, dated June 3, 1890.

Application tiled December 17, 1889. Serial No. 334,125. (No model.)

To all whom it may concern: radiation from the resistance is necessary in Be it known that I, CHARLES E. CARPENTER, order to dissipate its heat, which reacts therea citizen of the United States, residing at on, raising thetemperature thereof and caus- 5 5 Minneapolis, in the county of Hennepin and ing the same to become fused, thus destroy 5 State of Minnesota, have invented certain new ing its f unct-ion as a conductor of electricity and useful Improvements in lillectro-IIeating by reason of the consequent breaking of the Apparatus, of which the following1 is a specicircuit. lication. In the prior apparatus included in my afore- 6o This invention relates to improvements in said application I relied upon the elasticity 1o electro-heating apparatus for utilizing` the of the non-combustible heat-insulating filling heat developed by passing an electric current substance to continually produce the necesthrough a conductor of high resistance and sary pressure, so as to press the 'electricalinsmall capacity, but is more especially desulating substance to which the reflexed rc- 65 signed an improvement upon the invensistance is attached firmlyin the direction of x5 tion set forth in my application for Letters the heated surface-plate; but for the reasons Patent, Serial No. 319,900, filed August G, 1889, before stated I have found this method not since patented, No. 415,856, dated November satisfactory and eflicient under all conditions. 2G, 1839, in which, broadly speaking, the ap- It is well known that a substance in order 7o parat-us consisted of a body of any character, to be a good conductor of heat must have a zo a heated surface-plate therefor, an electrical loose and discontinuous structure, and if resistance lyingbetween said body and plate, firmly compressed, as is necessary in this case, a layer of electrical insulating material bebetween two surfaces with a pressure tending tween'said resistance and the plate, and a. to force them together, it would be rendered 75 layer of electrical insulating but non-heatmore compact and atthe same time,by reason 25 conducting material between said resistance of such compactness, become a better conand the body, and, in a more limited sense, ductor of heat. to a filling or packing of non-combustible The prime object of this invention thereheat-insulating material lying in a recess in fore is to intensify the heating effects pro- 8o thebody behind the elementsbefore specified` duced by passing a current of electricity 3o for the purpose of aiding in directing and through a conductor of high resistance and conlining the heat to the surface-plate. small capacity by subjecting the resistance to I find by experience that for the better and constant pressure, tending to firmly force the more eiiicient working of such apparatus it same toward the surface to be heated. S 5 is necessary to keep the heat-generating re- Another object is to avoid the occurrence 35 sistance in Iirm Contact with the electrical of air-spaces and the breaking of contact beinsulating sheet or substance, and in turn tween the resistance and the heated surfacethis electrical insulator in {irm contact with plate and thus prevent the fusion of the rethe heated surface-plate,not only for the wellsistance and the consequent breaking of the 9o known reason that heat is much more quickly electric current thereby. 4o and efficiently transmitted when the trans- A further object is to better confine the mitting bodies are under pressure, but be heat so generated to such part or parts only cause the filling of non-combustible heat-inof the body as may be desired by subjecting sulating materialnext thebody of theutensil, the active elements of the apparatus to con- 95 when used for some time, will shrink and ocstant pressure and at the same time inter- 4 5 cupy less space than when first put in place, posing between the active elements and the as a result of which, there being no pressure body a filling of heat-insulating material not upon the resistance-supporting card or layer under pressure. These objects are attained of material, the resistance at some points by the devices illustrated in the aceompanyroo will. fall away from the heated surfaceplate ing drawings, in which- 5o and no longer make contact therewith. lVhen Fi gurc l represents a plan View of a cookthis occurs, air-spaces are formed, and as the ing-stove or griddle-cake baker embodying heat cannot be transmitted by conduction my invention; Fig. 2, a similar view showing the top orheating plates of the stove removed, iiioi'e clearly disclosing the arrangement and disposition of the resistance for said plates; Fig. 3, an enlarged transverse section on the line 3 3 of Fig. l, illustrating sevei'al different means for pi'oduciiig pressure upon the resistance. Fig. 4 illust-rates the application of my invention to a laundi'y oi' other heating roller, and Fig. 5 the application of my invention to a sad-iroii.

Similar lettei's of reference indicate the same parts in the several figures of the drawings.

The apparatus shown in the drawings is similar to that illustrated in the drawings of my aforesaid application, both as to forni and application, and embodies the main features thereof in substantially the same arrangement and for the same purpose, for which reason I will only refer to these features generally which are common to all the forms.

Referring by letter to the accompanying draw'ings, let A represent the main body of the apparatus, whether stove, iron, or other forni of utensil in which such a body is de-Y sirable; B, the surface plate or plates to be heated, secured together by means of screws C or in any other well-known and convenient inannei', between which ai'e interposed, first, a card or sheet D of asbestus, cloth, or other suitable electric insulating' and non-heat-conducting' material, to the outer surface of which is secured a metallic i'esistaiice E, preferably consisting of wire of a refractory character reflexed back and forth over the surface of the asbestus sheet, as illustrated in Fig. and preferably secured thereto by any convenient forni of fastening, such as sewing with asbestus-thread, staples, or other suitable devices. lhis metallic resistance is separated from the heated sui'face-plate by another layer F, of substantially the saine size and contour' as the sheet- D, composed of some electi'ical insulating' substance which is iioii-combustible and of just suticient thickness to prevent the wire or other ,material used as a resistance from coming in contact with the surface-plate to be heatcd--such, for instance, as very thin asbestus-paper-it beingl understood that this sheet, while a non-conductor of electricity, should be a good conductor of heat, and should therefore furnish as great contactiiig-surface for the i'esistance-wire as possible. rlhe yielding character of asbestus-paper will permit the wire to sink into it so as to be partially encircled thereby, and thus afford the greatest contactarea for said wire for the transmission of its heat.

The body of the utensil should be hollow or recessed to a sufficient depth immediately back of the insulatingsheet D; but instead -of' filling this entire space with asbestus, firefelt, mineral wool, or some other substance which is a non-conductor of heat, as in my aforesaid application, I first provide one or two layers G of asbcstus fire-felt of substantially the same shape and contour as the sheet D, and a eompressure-plate ll of su lficient thickness to stand considerable pressure without springing pei'ceptibly, and which is forced toward the heated surface-plate by means of screws, springs, or any other equivalent devices for firmly pressing the resistance toward the surface-plate, this compressor-plate serving to bind the surface-plate, electrical insulatoi', resistance, the electrical insulator to which the resistance is secured, and the heatinsulating fire-felt firmly together into a conipaet body of active elements undei' considerable pressure, which may be regulated and varied at the will of the operator.

As before stated, the general features of construction ai'e similar to and their operation identical with the corresponding elements of my said prioi' application, the pui'- pose of which was to utilize the heat produced by passing a current of electricity through a conductor of high resistance and small capacity, and a detailed description of those features is not necessary; but this invention has for its object the further purpose of intensifying' the heat so produced by subjecting the resistance to a constant pressure, tending to foi'ce it firmly towai'd the heated surfaceplate, which may be accomplished by numerous devices and in various foi'ms of apparatus, sonic of which are illustrated in the drawings hereto attached, and which will now be described.

Referring more particularly to Figs. l and 3, it will be observed that the surface of the stove is divided into three principal pai'ts or sections, one of which is subdivided into two parts of half the dimensions of the original section and another into three parts circular in foi'm and corresponding to the lids of an ordinary stove, the main plate of the section in this ease constituting' asupport for the lids and is not intended to be heated, the heat being confined to the circulai' sections alone by the disposition of the resistance illustrated in Fig. 2, and the separation of the circular sections from the main body, as in my afoi'esaid application. ln this latter case the circular lids a are preferably provided with annular beveled flanges h, fitting' i nto corresponding openings c in the top or supportingplate of the section, the walls of which openings are beveled correspondingly with the flanges of the surface-plate, converging fi'oni the iniiei' to the outer surface of said plate, and provided with iiiwai'dly-projecting lugs e, against which the iiange of the surface-plate bears, so as to leave a space or opening bctween the surface and top plate at all points except where the lugs occur, and thus i'educe the contact between said plates, and colisequently the conduction of heat from the heated surface to the supporting or top plate. This surface-plate is held firmly in position, and the resistance and other active elements are forced firmly toward it by means of screws j', (shown in dotted lines in Fig. 3,) which IOO IIO

work th roughsaid plate and engage the compressor-plate Il, drawing the latter toward the surface plate, and thus transferring the weight of all the active elements to the surface-plate, from which they are suspended by the screws. In the center or rectangular section which is subdivided the same pressure is produced by screws; but in this case it is preferable that screw-heads should not break the continuity of the surface-plate g, 'for which reason they work through the compressorplate and the intervening layers without contact with the resistance, and screw into the surface-plate from the under side, in effect producing' the same result, however, as the screws in the first-described construction. In the third section, however, the pressure is shown as produced by means of a coil-spring h, confined between the compressor-plate and the bottom or body of the utensil, any number of which may be employed, the expansive force thereof tending to press the elements firmly together, the surface-plate in this case being fastened direct to the body of the utensil, so as to oppose the force of the springs.

In the case of the laundry or other heated roller illustrated in Fig. I the compressorplate may be formed in sections or dispensed with entirely, but preferably is of such form as to have self-contained compressor or eX- pansive force-such, for instance, as the coiled spring fz', fitting within the cylinder, the e pansive force of which tends to press the active elements outwardly, the su rface-plate, which in this caseis in the form of a cylinder or shell, being preferably secured to heads 7' by screws or otherwise, to which are secured the journals 7i; of the roller. Obviously, instead of the expausible coil-spring 'L' its wellknown equivalent in the form of an expansible-spring lining of sheet metal may be employed, and produces the same result. In both these forms the compressor performs the double function of a compressorplate and the screws, springs, or other devices for applying pressure thereto.

In the case of the sad-iron illustrated in Fig. 5 substantially the same construction as that applied to the central section of Fig I may be employed, and for the same reasons, the only difference being that the parts are inverted, but otherwise are exactly the same both in construction and operation. Obviously, the distance between the compressorplate and the heated surface-plate may be varied at will to accommodate differing thicknesscs of lire-felt or heat-insulating material, and also the pressure can be varied and the shrinkage of the various layers taken up, so as to prevent looseness thereof or air-spaces intervening therebetween.

For the purpose of better confining the heat to the surface-plate and to prevent the radiation of the heat from the compressor-plates, which will eventually become hot by reason of their confinement and the comparatively small amount of heat-insulating material between them and the heat-evolvin g resistance, l propose to lill the recesses in the body of the utensil behind the compressor-plate or the space intervening between it and the bottom of the utensil with some loose substance I-such as mineral wool, asbestus, or other good non-conductor of heatwhich structure by reason ofthe employment of the loose heatinsulating or non-conducting substance not under pressure almost perfectly prevents the escape of heat, so that the bottom of the utensil or the body thereof hardly ever becomes warm. The importance of this iilling for the purpose of confining the heat to the surfaceplate will be appreciated when it is known that the greater the quantity of tire-felting used between the compressor-plate and the resistance the greater will be the amount of heat absorbed thereby until the temperature thereof has reached a certain degree, as a result of which the heat forced toward the surface-plate is not as great or effective as it should be until the hre-felting or other hea-tinsulator has become quite thoroughly heated,

- for which reason I prefer to employ as little of the iire-felting as possible between the comln'essor-plate and the resistance, which I am enabled to do in the minimum amount by the use of this loose filling` of non-combustible heat-insulating material intervening between the compressor-plate and the body or bottom of the utensil. l

The principal advantage of employing pressure in a structure as herein described is that the shrinking of all the yielding elements may be readily taken up, so as to insure at all times a perfect contact between every part of the resistance and the heated surface-plate, it of course being understood that the electrical insulating-sheet always intervenes between the resistance and the surface-plate, so that the resistance cannot fall away at any point from the surface-plate and break contact therewith, for, should this occur, air-spaces would be formed, and as the heat cannot be transmitted to the surfaceplate by conduction radiation is necessary in order to dissipate the heat of the resistance which reacts upon the resistance, raising its temperature and causing the same to become fused, thus destroying its function as a conductor of electricity by the break in the circuit caused bysuch fusion.

Another advantage of the use of pressure in holding the active elements together is that the resistance will be buried or sunk into the insulator between it and the surfaceplate, and thus be furnished with the greatest possible contacting-area for the transmissionA of its heat, and at the same time reduces the thickness of the intervening electrical insulator to the minimumfdegree of thickness, leaving only just sufficient to serve as an electrical insulator without offering any material obstruction to the transmission of the heat.

IOO

IIO

Having described my invention, what I claim, and desire to secure by Letters Patent, is-

l. In an electro-heating apparatus, the combination, with the body, the heated surfaceplate thereof, an electrical resistance, a layer of electrical insulating` material between said resistance and plate, and a layerof electrical insulating;` non-heat-eondnoting material between said resista-nce and the body, of a compressor-plate lying` parallel with the surface-plate for forcing said resistance and layers toward the su rface-plate, substantially as described.

2. In an electro-heating' apparatus, the combination, with the body, the heated surfaceplate thereof, an elect-rical resistance, a layer of electrical insulating, material between said resistance and plate, and a layer of electrical insulating' non-heat-conducting material between said resistance and the body, of a conipressor-plate lying parallel with the surfaceplate forforeing said resistance, a layer of heat-insulating material interposed between said compressor-plate and the second layer of electrical insulating` material, and screws or their equivalent for 'forcing said compressorplate toward the`surface-plate, substantially as described.

23. In an electro-heating` apparatus, the combination, with the body, the heated surfaceplate thereof, a compressor-plate parallel with said surface-plate, and means for forcing` thc same toward the surface-plate, of an electrical resistance and electric insulators on each side thereof confined between said surface and said compressor plates, substantially as described.

4. In an electro-heating,` apparatus,thecombination, with the body provided with a recess therein, the heated surface-plate covering said recess, a cominessor-plate located in said recess lying; parallel with the surfaceplate, and a filling` of non-combustible heatinsulating material in said recess interposed between said compresser-plate and the body, of an electrical resistance and a layer of electrical insulating material on each side thereof confined between said compressor and surface plates, substantially as described.

5. In an electro-heating` apparatus, the combination, wit-h the body, the heating,I surfaceplate thereof, and a compressor-plate lying` parallel with said surface-plate, of an electrical resistance, a layer of electrical insulating material on each side thereof, and a layer of heat-insulating,l material between said members and the compressor-plate, all of which are confined between said compressor and surface plates, substantially as described.

(i. In an electro-heatingapparatus, the combination, with the body provided with a rccess, the heated surface-plate covering said recess, a compressor-plate located in said recess parallel with the surface-plate, and a fillingr ef non-combustible heat-insulating,y material in said recess between the compressor-plate and body, of an electrical resistance, a layer of electrical insulating' material on each side thereof, a layer of heat-insulating` material between said members and the compressor-plate, all of said members being' confined between the compressor and surface plates, substantially as described.

CHARLES E. CARPENTER.

viti'lessesz M. F. ScoinnLD, tenir. T. LANG. 

